Reinforcement of riveted electrical connections



ONS

DOMIZI ETAL REINFORCEMENT OF RIVETED ELECTRICAL CONNECTI Filed June 91958 m hm 3% INVENTORS ARIO DOMIZI G ORGE E. CRANCH ATTORNEY I nectionarises from the United States Patent Ofilice 3,056,057 Patented Sept.25, 1962 Filed June 9, 1958, Ser.

2 Claims. (Cl. 310-249) reinforced electrical connections and methods ofproducing the same. More particularly, this invention relates toreinforcing a riveted shunt connection to an electrical contact brush.

Riveted brush shunt connections have long been known to the art. Suchconnections are usually made by drilling a hole through the brush,counterboring the hole on one side of the brush, forming an eyelet orloop on the end of the shunt, placing the eyelet in the counterbore,inserting a tubular rivet blank through the eyelet and through thedrilled hole and then establishing the connection by spinning both endsof the blank to form rivet heads in situ.

A major disadvantage of this construction arises from the fact that itis difiicult to control the degree of mechanical tightness ofconnections at the proper level when manufacturing the riveted brushesin large quantity. If the rivet heads are not spun down tight enough,the connection may become easily loosened when the brush undergoesvibration encountered during service. When the rivet heads are spun downtoo tightly the relatively weak carbonaceous brush structure may crackin the area surrounding the counterbored rivet hole during the spinningoperation.

A further disadvantage of the riveted type brush conpracticalmanufacturing necessity of maintaining a reasonably large clearancebetween the body of the rivet and the drilled hole in the brush whenlarge numbers of connections are assembled. With this This inventionrelates to electrically useless and damage may even reach the point ofactual breakage of the brush at the point where the shunt is riveted. Ithas been found that by keeping the rivet itself fixed in relation to thebrush and allowing the brush and rivet to vibrate as a unit much of thestress on the brush at the rivet connection is relieved, and connectionlife is accordingly improved.

It is an object of this invention to provide a reinforced rivetconnection to an electrical contact brush.

It is another object of this invention to provide a method ofreinforcing a riveted brush connection which renders it relativelyinsensitive to normal vibration encountered during service.

In the accompanying drawings:

FIG. 1 is a perspective view of a brush embodying this invention withpart of the brush cut away;

FIG. 2 is similar to FIG. 1 showing one method of introducing areinforcing cement into a riveted brush connection;

FIG. 3 is similar to FIG. 2 showing another method of introducing thecement;

FIG. 4 is similar to FIG. 2 showing a further method of introducing thecement; and

FIG. 5 is similar to FIG. 2 showing still another method of introducingthe cement.

In accord with the above objects, this invention broadly comprises theprovision of a cementitious material beand the brush body of arivet-connected the cementitious material may generally be of any typeand it may be introduced between the rivet and the brush body by avariety of means,

certain materials introduced in particular ways have been found toperform very well in the practice of this invention.

Organic cements, such as self-hardening polymeric materials of thethermosetting type, mineral cements and molten metals, which solidifyupon cooling to above the brush operating temperature, have been foundto be entirely satisfactory materials. Any of these may be suitablyprovided between the brush body and the rivet by any of the meanshereinbelow described with reference to the accompanying drawing.

A complete reinforced riveted connection is shown in FIG. 1

terminates the electrical shunt 14. A metal shank washer 16 is placedover the cable eyelet, and a hollow rivet blank 17 is inserted throughthe eyelet-shank washerbrush body assembly. A metal washer 15 is placedover the rivet blank 17 and against the brush body 10 opposite the sideof said brush body 10 having said counterbore recess. The rivet heads 18and 19 are then formed by spinning, thus securely holding the eyelet 12in intimate contact with the brush body at the interface 20. Of course,one head of the rivet blank 17 may be spun prior to insertion of saidrivet blank 17 into said hole in said brush body 10. In this case, theassembly is bound to intimate contact by spinning the remaining unspunend of spinning both heads at once, as described above. The cement 22may be introduced into the assembly in a variety of ways.

Referring to FIG. 2, for example, the cement 22 may be introducedbetween the rivet body 17 and the brush body 10 through a hole 24 in therivet 17 after the rivet heads 18 and 19 are spun. Or, as shown in FIG.3 the cement 22 may be introduced between the rivet 17 and the brushbody 10 through a hollow needle 28 inserted parallel with the electricallead 14. Here again, the cement 22 is inserted after the rivet heads 18and 19 are In the modification illustrated by FIG. 4, the cement 22 isintroduced between the rivet '17 and the brush body 10 through a hole 30in the brush body 10 which extends to the rivet 17. The cement 22 isinserted after the rivet heads 18 and 19 are spun in place. Another wayof practicing the invention is illustrated in FIG. 5, where the cement22 is coated on the rivet body 17 prior to insertion thereof into thebrush body 10. The rivet 17 with one head 19 spun, is then inserted andthe other head 18 is spun in place.

In each case, the cement is hardened in situ after the electricalconnection has been secured by the rivet.

It is an important consideration in the practice of this In order toprotect against this contingency, the cementitious material shouldpreferably be added after the rivet is in place and good electricalcontact has been established. Another important consideration of thisinvention is the choice of the materials to secure the rivet to thebrush body.

range of the brush may be used successfully.

Examples of some of these materials are melaminealdehyde condensationproducts, epoxy and polyester resins, solidified metals added in themolten state, acrylonitrile polymers and others. Insome cases it isfound advantageous to incorporate inorganic materials in the brushes ofconventional'riveted construction. The data taken from, these testsshowed that brushes reinforced with" a cementitious materialaccording tothis invention had an average life of 11 million impacts beforeloosening occurred. Conventional rivet connected brushes tested underthesame conditions lasted through an average; of only940 thousand impactsbefore loosening occurred. Thus, it may be readily seen that the usefullife of rivet connectedbrushes made according to this inventionwas about12 times that of conventionally riveted brushes.

What is claimed is:

1. In a riveted electrical brush connection which comprises a brush bodyprovided with a hole therethrough and an eyelet of an electrical shuntseated over and around, said hole, said brush body and said eyelet ofsaid shunt being bound together by a rivet which extends through saidhole and which-is"spun"overontosaidcom nection at both ends thereof; theimprovement which comprises a cementitious material located between saidbrush body and said rivet and in contact with substantially the entireadjacent surfaces of said brush body and said rivet.

2. The improvement as defined in claim 1 wherein said cementitiousmaterial is chosen from'the group consisting of a self-hardeningplastic, a thermo-setting resin, a phenol-formaldehyde condensationproduct, and a metallic material which remainsa solid at the operatingtemperature of said connection.

References Cited in the tile of this patent UNITED STATES PAT ENTS847,303 Platt Mar: "12; 1907 1,585,849 Gindre May 25, 1926 1,848,142Pierce Mar. 8, 1932 1,929,142 Hosfield Oct. 3, 1933- 1,970,022 Pietenpolet al. Aug. 14, 1934 2,199,532 Weeks May 7, 1940 2,237,474 Channell Apr.8, 1941 2,342,732 Gudrnundson Feb. 29, 1944 2,507,780 Gilbert May 16,1950' 2,849,631 Matz Aug. 26, 1958 FOREIGN PATENTS 451,714.GreatlBritain Aug, 11; 1936

